If you are going to buy and hold, MFH is a better long term choice, but you are right to be concened, if not local, your team and resources will make or break the deal. 

"BiggerPockets" is a popular choice, offering a wealth of information from industry experts.Networking: Joining local real estate investment groups or online forums can be incredibly beneficial.

I think in most markets, 3 nicely appointed modest properties will perform over the long run better than a big fancy one.If I had my choice, I would have 3 lake houses like I have now rather than a single lake mansion.

So at that point you risk dealing with very high vacancy rate or you have to find an alternative solution. 

However, since I haven't gotten an LTR in there, my choices now are to relist it for sale (the market is slowing), or invest $15k or more into furnishing it.

I’m also in the lending space and have seen how financing choices shape outcomes, so feel free to connect if you want to share more ideas.

Relocators can be good choices for you too. 

The best choice depends on how much control you want to keep and what type of return your investors are looking for.

that's the question to be addressed - opportunity zones as an alternative for 1031s?

Yes, you're missing the underlying appreciation of the house, the value of storing money in a physical asset versus an alternative and capex costs.